New drugs to find the right target to fight Alzheimer's disease

August 2, 2013

The future is looking good for drugs designed to combat Alzheimer's disease. EPFL scientists have unveiled how two classes of drug compounds currently in clinical trials work to fight the disease. Their research suggests that these compounds target the disease-causing peptides with high precision and with minimal side-effects. At the same time, the scientists offer a molecular explanation for early-onset hereditary forms of Alzheimer's, which can strike as early as thirty years of age. The conclusions of their research, which has been published in the journal Nature Communications, are very encouraging regarding the future of therapeutic means that could keep Alzheimer's disease in check.

Alzheimer's disease is characterized by an aggregation of small biological molecules known as amyloid peptides. We all produce these molecules; they play an essential antioxidant role. But in people with Alzheimer's disease, these peptides aggregate in the brain into toxic plaques – called "amyloid plaques" – that destroy the surrounding neurons.

The process starts with a long protein, "APP", which is located across the neuron's membrane. This protein is cut into several pieces by an enzyme, much like a ribbon is cut by scissors. The initial cut generates a smaller intracellular protein that plays a useful role in the neuron. Another cut releases the rest of APP outside the cell – this part is the amyloid peptide.

For reasons not yet well understood, APP protein can be cut in several different places, producing amyloid peptides that are of varying lengths. Only the longer forms of the amyloid peptide carry the risk of aggregating into plaques, and people with Alzheimer's disease produce an abnormally high number of these.

A favorite Alzheimer's target: gamma secretase

The two next-generation classes of compound that are currently in clinical trials target an enzyme that cuts APP, known as gamma secretase. Until now, our understanding of the mechanism involved has been lacking. But with this work, the EPFL researchers were able to shed some more light on it by determining how the drug compounds affect gamma secretase and its cutting activity.

In most forms of Alzheimer's, abnormally large quantities of the long amyloid peptide 42 – named like that because it contains 42 amino acids – are formed. The drug compounds change the location where gamma secretase cuts the APP protein, thus producing amyloid peptide 38 instead of 42, which is shorter and does not aggregate into neurotoxic plaques.

Compared to previous therapeutic efforts, this is considerable progress. In 2010, Phase III clinical trials had to be abandoned, because the compound being tested inhibited gamma-secretase's function across the board, meaning that the enzyme was also deactivated in essential cellular differentiation processes, resulting to side-effects like in gastrointestinal bleeding and skin cancer.

"Scientists have been trying to target gamma secretase to treat Alzheimer's for over a decade," explains Patrick Fraering, senior author on the study and Merck Serono Chair of Neurosciences at EPFL. "Our work suggests that next-generation molecules, by modulating rather than inhibiting the enzyme, could have few, if any, side-effects. It is tremendously encouraging."

New insights into hereditary forms of the disease

During their investigation, the scientists also identified possible causes behind some hereditary forms of Alzheimer's disease. Early-onset Alzheimer's can appear as early as thirty years of age, with a life expectancy of only a few years. In vitro experiments and numerical simulations show that in early-onset patients, mutations in the APP protein gene modify the way by which APP is cut by the gamma-secretase enzyme. This results in overproduction of amyloid peptide 42, which then aggregates into amyloid plaques.

This research illuminates much that is unknown about Alzheimer's disease. "We have obtained extraordinary knowledge about how gamma secretase can be modulated," explains co-author Dirk Beher, scientific director of Asceneuron, a spin-off of Merck Serono, the pharmaceutical division of Merck KGaA, Darmstadt, Germany. "This knowledge will be invaluable for developing even better targeted drugs to fight the disease."

Related Stories

Blocking a transport pathway through the brain cells offers new prospects to prevent the development of Alzheimer's. Wim Annaert and colleagues of VIB and K.U. Leuven discovered that two main agents involved in the inception ...

New research reveals that the likely culprit behind Alzheimer's disease has a different molecular structure than current drugs' target—perhaps explaining why these medications produce little improvement in patients.

Scientists from VIB and KU Leuven have discovered a new target molecule for the development of a treatment against Alzheimer's disease. There is currently no cure for this disease. Many candidate drugs fail because they also ...

Researchers in Berlin and Munich, Germany and Oxford, United Kingdom, have revealed that a protein well known for its role in Alzheimer's disease controls spindle development in muscle and leads to impaired movement in mice ...

The molecular structure of a protein involved in Alzheimer's disease  and the surprising discovery that it binds cholesterol  could lead to new therapeutics for the disease, Vanderbilt University investigators ...

Recommended for you

Cedars-Sinai neuroscience investigators have found that Alzheimer's disease affects the retina—the back of the eye—similarly to the way it affects the brain. The study also revealed that an investigational, noninvasive ...

By the time you start losing your memory, it's almost too late. That's because the damage to your brain associated with Alzheimer's disease (AD) may already have been going on for as long as twenty years. Which is why there ...

A new machine learning program developed by researchers at Case Western Reserve University appears to outperform other methods for diagnosing Alzheimer's disease before symptoms begin to interfere with every day living, initial ...

In a study looking at brain scans of people with mild loss of thought and memory ability, Johns Hopkins researchers report evidence of lower levels of the serotonin transporter—a natural brain chemical that regulates mood, ...

People with specific mutations in the gene TREM2 are three times more likely to develop Alzheimer's disease than those who carry more common variants of the gene. But until now, scientists had no explanation for the link.

Researchers from Yale University School of Medicine have discovered that defects in the transport of lysosomes within neurons promote the buildup of protein aggregates in the brains of mice with Alzheimer's disease. The study, ...

0 comments

Please sign in to add a comment.
Registration is free, and takes less than a minute.
Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.